Study of a fluorine-free silane-based film on an aluminum alloy via drop-coating method with the purpose of providing hydrophobic and corrosion protection properties

This work sought to developed a fluorine-free, water-repellent silane-based film on 5052 aluminum alloy by studying the incorporation of Hexadecyltrimethoxysilane (HDTMS) into or over the silica gel film to protect against corrosion in a saline environment. Additionally, the interface of the silane-based film was studied using liquids such as soybean oil, diesel oil, and lubricating oil. Silica gel particles were deposited by dripping a solution of silica gel using design of experiment approach. The porosity of the silica gel film was assessed employing the potentiodynamic polarization technique. The condition of the more cohesive silica gel film was chemically modified by dripping a low concentration solution of HDTMS. The functionalized film on the aluminum alloy exhibited a contact angle of 136°, oleophilic behavior for soybean oil and lubricating oil, and superoleophilic character for diesel oil. Notably, hydrophobic film exhibited chemical (acid, alkaline, saline) and thermal stabilities (50–150 °C). The protective effect of the functionalized film against corrosion ions was confirmed by Electrochemical Impedance Spectroscopy in a saline solution over 7 days. These results suggest a fluorine-free alternative approach for thin film development and the study of its multifunctionality, including enhanced corrosion resistance, water-diesel oil separation, and potential applications in anti-fouling.